Mitllari, Eralda, and Mimoza Kasimati. “Is Preference for Monetary Nonmonetary Rewards Related With the Level of Income?”. European Scientific Journal, ESJ 15, no. 4 (February 28, 2019): 215. Accessed April 18, 2025. https://test.eujournal.org/index.php/esj/article/view/11767.